The host-environment dialogue is appreciated to influence the development of inflammatory and autoimmune- mediated diseases, including that of type-1 diabetes (T1D); however, the specific aberrant host-environmental dialogues are poorly understood. In addition, while it is clear that environmental factors are important for disease development, studies have focused on a unidirectional, environmentally-driven dialogue. Instead, I propose that rather than the specific nature of environmental triggers, the way in which such environmental signals are perceived in individuals susceptible to T1D is most important to disease initiation and/or progression. By focusing on defects in the way a host interprets environmental signals, the proposed studies can explain development of a common disease phenotype (T1D) despite heterogeneous environmental triggers in different individuals. The gastrointestinal (GI) tract is the largest single environmental interface of the human body, and is a major site of immune activation and tolerance induction. The summation of information received at the intestinal interface dictates a delicate balance among protective immunity, inflammation, and tolerance. In addition, as a first line of defense, intestinal epithelial cells (IECs) have the ability to participate in immune regulation. Thus, here I propose to investigate T1D-specific host-environment dialogues at the intestinal epithelial cell interface. I hypothesize that in T1D, aberrant IEC-mediated microbial sensing induces an inflammatory rather than a tolerogenic environment within the gastrointestinal tract and precipitates a break in tolerance to self-antigens. To date, lack of robust primary intestinal epithelial cell (IEC) culture has hindere advancement of knowledge in this arena. We have overcome this hurdle through the successful isolation and culture of primary IECs from human cadaver donors as well as murine models. Using our novel culture systems, I aim to evaluate and elucidate the dynamics of microbial-sensing defects in the intestine in T1D throughout the course of disease progression and correlate these dynamics with changes in resident immune cell phenotype and function. Importantly I aim to delineate the mechanisms associated with alterations in microbial induced responsiveness observed. The significance of this research is that it will provide understanding of mechanisms by which IEC interactions with the environment either initiate or enhance T1D. The innovation of this research lies in the tools we have developed which will allow us to elegantly address the questions posed above. In summary, successful completion of these studies will provide much needed insight into mechanisms of intestinal homeostasis and the contribution of the intestinal environment in the development of T1D. Advances in understanding initiating events at the intestinal level may also aid therapeutic approaches aimed at oral tolerance.